It’s only been about a year since the tropical disease chikungunya was first spotted in the Western Hemisphere. In December 2013, the U.S. Centers for Disease Control issued a travel warning to the Caribbean after the disease had been found on the island of St. Martin. Since then, there have been more than a million cases in the Americas, including confirmed cases in Florida, North Carolina, and other states.
Chikungunya causes fever, fatigue, and joint swelling, and is transmitted by the Asian tiger mosquito, Aedes albopictus. When the disease arrived in Panama, scientists at the Smithsonian Institution decided to examine how human activity spreads the Asian tiger mosquito. Their findings appear in an article in PLOS Neglected Tropical Diseases.
Panamanian health authorities first detected the Asian tiger mosquito in 2002 and kept tabs on its spread from Panama City. This comprehensive data — uncommon in many tropical nations — coupled with years of mosquito surveys by the Smithsonian Tropical Research Institute, showed that the Asian tiger mosquito relies on road networks to disperse.
“The vector is not moving organically across the landscape,” said Matthew Miller, lead author of the study.
To stem the mosquito’s spread, the authors recommend health authorities fumigate vehicles at checkpoints that are already set up throughout Panama to prevent screwworms from spreading from Colombia to North America. Checkpoint fumigation could prevent the Asian tiger mosquito from reaching areas where it has not been detected.
Nature abhors a vacuum
In May 2014, Panama allowed a British company called Oxitec to release sterile yellowfever mosquitoes (Aedes aegypti) in order to combat dengue, another disease that is vectored by mosquitoes.
However, the Smithsonian scientists say that as the Aedes aegypti populations decrease, they may be replaced by Aedes albopictus because the Asian tiger mosquito could fill the niche that the yellowfever mosquitoes occupied.
“The two mosquito species are so ecologically similar that, by depressing Aedes aegypti populations, the chances that Aedes albopictus is going to competitively displace it may increase,” said Miller. “This research is relevant to the study of introduced disease vectors everywhere.”
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